The signaling of alarms from remote locations over communication lines to an administration bureau is well known in the prior art. Typically, facilities at the administration bureau are arranged to examine the communication lines to sense impedance conditions thereon which signify the presence or absence of an alarm.
One of the problems in such an arrangement is that an occasional fault condition, such as an open or short on a signaling line conductor interferes with accurate alarm sensing and detection. The interference reduces the integrity and reliability of the alarm system and tends adversely to affect the safety of protected personnel and premises. The National Fire Protection Association (NFPA) recognizing those deficiencies has established regulations for the detection of an alarm despite the presence of an open or shorted conductor of the signaling line used for reporting the occurrence of that alarm.